[LOG4J2-2725] RingBufferLogEvent.clear() is not called in case of OutOfMemoryError (or any other exception/error)

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.12.1
• Fix Version/s: 2.13.0
• Component/s: Core
• Labels: OOM
• Assignee: Unassigned
• Reporter: Dzmitry Anikechanka
• Created: 18/Nov/19 08:36
• Updated: 20/Feb/20 23:21
• Resolved: 08/Dec/19 02:56

Description

Please see the following class https://logging.apache.org/log4j/2.x/log4j-core/apidocs/src-html/org/apache/logging/log4j/core/async/RingBufferLogEventHandler.html

There is the following code in the onEvent() method:

event.execute(endOfBatch);
event.clear();

But in case of an exception (or error) in the execute() method - method clear() will not be invoked, event will be not cleared (and logged message as well) and will be in the memory (probably try/catch will be enough to fix the issue).

I've faced this issue when OutOfMemoryError occurred due to very large messages logging (also message is duplication in the SimpleMessage class, please see related issue https://issues.apache.org/jira/browse/LOG4J2-2724) - all these event are still in memory and it causes a lot of another OOM errors as memory is not released (because clear() method was not invoked).

Please see attached RingBufferLogEvent_dominator_tree.txt report from Eclipse Memory Analyzer (https://www.eclipse.org/mat/). As you can see there are a log of RingBufferLogEvent object that were not cleared and garbage collected:

Class Name                                                                                    | Shallow Heap | Retained Heap | Percentage
------------------------------------------------------------------------------------------------------------------------------------------
                                                                                              |              |               |           
com.lmax.disruptor.RingBuffer @ 0x9f29a550                                                    |          144 | 1,205,392,112 |     57.52%
'- java.lang.Object[262208] @ 0xb3d00000                                                      |    1,048,848 | 1,205,391,968 |     57.52%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0xa35f7f08                     |          104 |   233,251,104 |     11.13%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x8727b4d8                     |          104 |   185,151,488 |      8.84%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x8728ef48                     |          104 |   115,523,080 |      5.51%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x87264ae0                     |          104 |    83,109,992 |      3.97%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0xb1bd6950                     |          104 |    69,825,312 |      3.33%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x872730d0                     |          104 |    67,399,704 |      3.22%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x872651c8                     |          104 |    67,209,496 |      3.21%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x828e61d8                     |          104 |    48,321,480 |      2.31%
   |- org.apache.logging.log4j.core.async.RingBufferLogEvent @ 0x828ca708                     |          104 |    42,499,912 |      2.03% 
................

Also please see RingBufferLogEvent_OOM.log log file with OOM stacktrace:

java.lang.OutOfMemoryError: Java heap spacejava.lang.OutOfMemoryError: Java heap space at java.util.Arrays.copyOf(Arrays.java:3332) at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:137) at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:121) at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:421) at java.lang.StringBuilder.append(StringBuilder.java:136) at org.apache.logging.log4j.core.pattern.LineSeparatorPatternConverter.format(LineSeparatorPatternConverter.java:66) at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:38) at org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializable(PatternLayout.java:333) at org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:232) at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:217) at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:57) at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:177) at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:170) at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:161) at org.apache.logging.log4j.core.appender.RollingFileAppender.append(RollingFileAppender.java:268) at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:156) at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:129) at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:120) at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84) at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:448) at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:433) at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:417) at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:79) at org.apache.logging.log4j.core.async.AsyncLogger.actualAsyncLog(AsyncLogger.java:337) at org.apache.logging.log4j.core.async.RingBufferLogEvent.execute(RingBufferLogEvent.java:161) at org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:45) at org.apache.logging.log4j.core.async.RingBufferLogEventHandler.onEvent(RingBufferLogEventHandler.java:29) at com.lmax.disruptor.BatchEventProcessor.run(BatchEventProcessor.java:129) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) 

Could you please fix it or explain if such behavior is expected?

Thanks,
Dzmitry

Issue Links

• relates to: LOG4J2-2724 SimpleMessage - message duplication (String and CharSequence fields)
• links to: GitHub Pull Request #316
• links to: GitHub Pull Request #317